Here's my theory about why the one on the left looks better to some: Given that this is a physical poster, I think we've come to expect a certain crammed format that we've already learnt how to navigate well (think classifieds). So it no longer feels strange or crammed.
Question for those who think the left one is cleaner: what if this was a web page? You need to look at each one zoomed-in one at a time. Would you still consider the left one cleaner?